Man in custody over fatal stabbing in Sydney suburb of Berala

A man is dead and another is in police custody after a stabbing in Sydney's west overnight.

Police were called to reports of a disturbance at a unit on The Crescent at Berala around 2am (AEST).

They found two men who had been stabbed.

The men were taken to Westmead Hospital, but one of them died a short time later.

A third man was arrested at the unit.

The 36-year-old was taken to Auburn Police Station for questioning.

Police say the man is an Iranian citizen who was born in Afghanistan.

They say the three men all lived in the unit, along with two others.

Detective Inspector Paul Arnold says there have been language barriers so far in the investigation.

"We've got no knowledge of the relationship of the five men that live at the unit," he said.

"We're experiencing quite an amount of difficulty due to the fact that the people come from Afghanistan and we're having issues in relation to sourcing the correct dialect interpreters."

Neighbours have reported hearing screaming and arguing before police arrived at the unit.

The ages of the victims are not yet known.

Morrison questions Burke over case

The federal Opposition's immigration spokesman, Scott Morrison, has seized on the case.

Mr Morrison says the Department of Immigration and Citizenship has provided initial advice that the arrested man is an asylum seeker on a bridging visa.

"This is a very concerning and a very disturbing development," Mr Morrison said.

"I think it's important that the Minister for Immigration throughout the course of the day and the sooner the better, once these facts are able to be established, can confirm the facts in this case and can confirm the status of the individual and what the Government's response to these incidents are.

"Police who were called out to this incident last night would have no knowledge of the immigration status of the people behind that door.

"It is the Coalition's policy that any person on a bridging visa that has been released into the community, their address details would be available to the police."

But Immigration Minister Tony Burke has rejected Mr Morrison's demands and accused him of trying to politicise the issue.

He says any further information released about the arrested man should be determined by police, not federal politicians two days before an election.

Detective Inspector Arnold says the man's immigration status is not the primary focus of the investigation.

"What we're interested in is establishing the nature of the events that took place," he said.